java.util.ConcurrentModificationException observed in unreserving slots for HiRam Jobs

Ran jobs out which 3 were HiRAM, the job were not removed from scheduler queue even after they successfully completed
hadoop queue -info queue -showJobs displays somwthing like -:
job_200907080724_0031 2 1247059146868 username NORMAL 0 running map tasks using 0 map slots. 0 additional slots reserved. 0 running reduce tasks using 0 reduce slots. 60 additional slots reserved.
job_200907080724_0030 2 1247059146972 username NORMAL 0 running map tasks using 0 map slots. 0 additional slots reserved. 0 running reduce tasks using 0 reduce slots. 60 additional slots reserved.

But it does not block anything, but seems like zombie process of system
Jobtracker log show java.util.ConcurrentModificationException